1. Field of the Invention
The present invention relates to the field of cosmetically improving and altering the appearance of teeth.
2. Brief Description of the Prior Art
Many procedures are done to improve the appearance of teeth. Teeth are filled to replace dentin and enamel invaded by bacteria, and can be capped to replicate a removed or abraded portion of a tooth.
The teeth of individuals widely vary in their appearance and shape. This is due to the genetic make-up of the individual, but can also be affected by age, and the degree of contact with various foods and medications, both those superficially contacting the teeth and from the internal effects of the medication. The teeth of some individuals exhibit a yellow appearance while those of others may be whiter. While aging is often considered a "natural" cause of tooth discoloration, other factors commonly attributed to tooth discoloration can include chemical exposure to tannins, which are found in red wines, and brewed beverages such as coffees and teas. Additional discoloring chemicals include those not naturally occurring in foods, but rather, manufactured or synthesized compounds, such as, for example, the compounds found in medications, like antibiotics, including tetracycline and other pharmaceuticals. The common practice of using doses of tetracycline to cure facial, acne blemishes has been known to contribute to the discoloration of teeth. Aside from these chemicals, even excess brushing has been can create discoloration by repeated contact with fluoride compounds commonly present in most toothpastes.
Many have attempted to confront the problem of tooth discoloration by proposing various solutions to whiten the teeth. One such method of tooth whitening involves the bonding of veneers onto the buccal or labial surfaces of a tooth. The veneer is usually constructed and applied by a dentist using dental bonding techniques to attach it to the tooth. Various veneers have been described in several U.S. Pat. Nos., see, e.g. 4,992,049 "Method for Applying a Veneer Facing to a Tooth"; 4,822,279 "Article for Cosmetic Restoration of Anterior Teeth" (which uses a glazed porcelain labial veneer); 4,682,950 "Device and Method of Bonding and Veneering Dental Material to a Tooth" (syringing composite material to a tooth surface which has been etched and coated with a bonding material); 4,473,353 "Method for Cosmetic Restoration of Anterior Teeth" (wherein a glazed porcelain veneer is bonded to a patient's tooth); and 4,433,959 "Composite Laminate Dental Veneer Containing Color Systems" (a veneer which is molded and then attached to the labial enamel surfaces of teeth).
Other attempts to whiten teeth are also known to include bleaching the teeth. Often the bleach is applied in the form of hydrogen peroxide, which can be obtained in drug stores by consumers. Because of the delicacy of applying hydrogen peroxide in one's mouth, some dentists carry out the procedure in their offices, using a stronger peroxide than can be purchased by the consumer. There are even pastes, sold over the counter, to the consumers which claim to whiten teeth. Often ordinary toothpastes make this claim, but increasingly appearing in the marketplace for purchase by consumers are pastes with the chemical compound sodium bicarbonate (baking soda), which may also contain peroxide. While chemical bleaching of teeth has been done to provide whiter-looking teeth, with its use there exists danger to the enamel of the teeth, especially if excessive exposure to chemical bleaches occurs. Further, chemical bleaching is understood in many cases to require multiple applications, and, hence, repeated use of the chemical. Even when applied by a dentist, precautions may be taken to prevent peroxide solution from contacting the patient's gums, which if otherwise allowed to come into contact therewith can be painful and cause damage to the gums. In cases of certain stains, bleaching may not be effective, and the stain may remain.
There are even procedures involving abrasion of the tooth enamel to present a smooth surface which is lighter in appearance than the stained surface removed. This has limitations as to the number of times it can be done.
Furthermore, abrading or bleaching teeth can have deleterious side effects, including, increased sensitivity of the treated tooth to temperature, i.e. especially when hot and cold foods and drinks are consumed. This effect may subside within time, but often the need to repeat bleaching procedures regularly, gives rise to a period of time within which the treated tooth can be hypersensitive.
There are some prior art whitening methods which require etching steps that are carried out with phosphoric acids. The use of phosphoric acid is generally done by a dentist under controlled conditions, for example, in the dentist's office. Caustic acid etchants have been recognized to be corrosive to the soft tissues of the mouth. For example, ortho-phosphoric acid, in some venues, must be transported pursuant to specified requirements and restrictions. In addition, the long term physiological effects of acid etching, which are generally unknown, have led practitioners to question certain acid etching uses in the field of dentistry. See e.g. M. G. Buonocore, "The Challenge of Bonding to Dentin", The Acid Etch Technique, L. M. Silverstone and I. L.Dogon, Eds., Proceedings of the International Symposium at St. Moritz, Switzerland, Dec. 16-18, 1974, North Central Publishing Co. (St. Paul, 1975). See also, U.S. Pat. No. 5,304,585, which raises these concerns, the complete disclosure of which is herein incorporated by reference; and see Akira Komori, and Haruo Ishikawa, "Evaluation of a Resin-Reinforced Glass Ionomer Cement for Use as an Orthodontic Bonding Agent," The Angle Orthodontist, Vol. 67 No. 3, 1997, the complete disclosure of which is herein incorporated by reference. Further attempts to whiten teeth are disclosed in U.S. Pat. Nos. 4,032,627 "Tooth Whitening Cosmetic Composition"; 4,097,994 "Dental Restorative Composition Containing Oligomeric Bis-GMA Resin and Michler's Ketone"; 4,141,144 "Dental Material and Method For Controlling Tooth Lustre"; and 4,512,743 "Method for Masking Discoloration on Teeth." U.S. Pat. Nos. 4,512,743 and 4,141,144, each use phosphoric acid application to the tooth in their treatments. U.S. Pat. No. 4,097,994 discloses a photocurable compound, which is used with a specific ultraviolet sensitizer and a peroxide catalyst to cure the compound. Furthermore, phosphoric acid etching generally disposes grooves in the tooth enamel in the nature of about 50 to 60 .mu.m. This order of etching is visible and is noticed in the form of a dull tooth surface.
U.S. Pat. No. 4,032,627, referenced above, discloses the use of an alcohol-soluble composition to be applied to the surface of a tooth to whiten the tooth's appearance. This composition is suggested to be applied by the user. However, although this disclosure attempts to provide an extended wearing time for its compound, the composition is readily worn off by the abrasive action of food eaten after the compound is applied to the teeth, with certain, more abrasive, harder, foods causing faster wear of the composition from the tooth than other, softer, foods.
A need exists for a temporary tooth whitening and colorizing system which can be safely applied by the wearer, or without the need for specially trained dental personnel. The tooth whitening to be achieved should also have stability and be able to resist removal or solvation by foods and beverages, but should be able to be removed whenever the user desires. It is further desirable to provide a composition and a method for covering a tooth, to appear white or colorized, which can be selectively applied and removed by a wearer without harming the tooth.